asp.net 生成验证码

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;
using System.Drawing.Imaging;

namespace test
{
    public partial class verCode : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                GenerateCode();
            }
        }



        private void GenerateCode()
        {
            Random r = new Random();
            string code = "";

            for (int i = 0; i < 5; i++)
            {
                code += r.Next(0, 10);
            }

            //字体
            string[] fonts = { "微软雅黑","宋体","黑体","仿宋","隶书"};
            //字体颜色
            Color[] colors = { Color.Red,Color.Black,Color.Blue,Color.Orange,Color.Yellow };
            //创建位图
            Bitmap bmp = new Bitmap(100, 30);
            //创建GDI
            Graphics g = Graphics.FromImage(bmp);
            //清空画布
            g.Clear(Color.White);

            //创建画笔
            Pen pen = new Pen(Color.Green);
            //设置线的宽度
            pen.Width = 2;

            //划线添加干扰
            for (int i = 0; i < 50; i++)
            {
                Point p1 = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));

                Point p2 = new Point(r.Next(0, bmp.Width), r.Next(0, bmp.Height));
                //划线
                g.DrawLine(pen, p1, p2);
            }

            for (int i = 0; i < 5; i++)
            {
                Font font = new Font(fonts[r.Next(0,5)],20,FontStyle.Bold);

                SolidBrush brush = new SolidBrush(colors[r.Next(0,5)]);

                Point p = new Point(i*20,0);
                //画文本内容
                g.DrawString(code[i].ToString(),font,brush,p);
                
            }
            
            //添加斑点

            for (int i = 0; i < 500; i++)
            {
                //对位图添加斑点
                bmp.SetPixel(r.Next(0,bmp.Width),r.Next(0,bmp.Height),Color.Lime);
            }

            
            //保存位图
            bmp.Save(Response.OutputStream, ImageFormat.Gif);

            //设置相应类型
            Response.ContentType = "image/gif";

            bmp.Dispose();

            g.Dispose();


        }
    }
}